Often hailed as the worst film ever made, Plan 9 From Outer Space is definitely an experience. If you had to pay so much as a penny to see it, the cost-proposition might be rough, considering the so-bad-it's-good here really skirts the edge of venturing into so-bad-it's-bad.
Fortunately (?) for all of us, it is available for free on YouTube. The only cost is 1 hour, 18 minutes, and 21 seconds of your time. If you are comprised of 50 percent irony and 50 percent the-urge-to-criticize-and-revel-in-the-awful, as so many of us Internet dwellers are, it's worth at least a little of your time. In it's original form, it pairs nicely with a side of TVTropes, but if you can't handle it straight, the Rifftrax version is available (also for free) on Hulu. Good luck; you'll be a better person for the experience, I think. [YouTube, Hulu]